Sounds good! First, if you’re starting running now, get yourself onto tracking your runs in kilometres, not miles.
Personally, if I feel like I’ve started a 5km run too quickly, I dread that I won’t make it to the end. If I give up or slow down massively before 3.5km, I just head home. But if I reach 3.5km, I know I can push through to the end. I feel like having a goal of a set distance in certain time is what works best, not running until I’m too tired or, god forbid, injured. The best thing is, as I get better, the exercise takes less time, not more, compared to those aiming for longer distances.
Training and general fitness are well known (proven) to help with anxiety, but I have seen it become so much of a coping mechanism that it becomes an obsession. And, as I’ve seen this in my own family members with mental health issues, I feel I have to consciously guard myself against it. As soon as I start to think “Maybe I should start training for a marathon…” STOP! I do not need that in my brain.